FROM THE TERTIARY LAVAS AROUND BEN MORE, MULL. 5 



walls which, when examined closely with a lens, show a fine set of striae formed by 

 two sets of lines intersectino; at about 60°. There can be little doubt that these 

 cracks were once filled with calcite, which has left its cleavage traces on the 

 adjacent scolecite. The following analysis was made by Mr E. G. Eadley in 

 the laboratory of the Geological Survey : — 











Calculated for Formula 











CaAl 2 Si 3 O 10 + 3H 2 0. 



Si0 2 . 



. 46-10 



per 



cent. 



45-9 



A1A . . . 



25-05 





>> 



26-0 



Fe 2 3 . 



•55 





» 





CaO . 



14-17 





>> 



14-3 



MgO . 



•32 





>> 





K,0 . 



•03 





> 



... 



Na 2 . 



trace 







... 



H 2 at 105° C. . 



•13 



per 



cent. 





H 2 above 105° C. 



. 1378 





;> 



13-8 





100-13 



per 



cent. 



ioo-o 



The mineral is thus a typical scolecite practically free from alkalies. 



The junction of the zeolite with the walls of the vesicle presents some interesting 

 and unusual features. In place of the layer of green earth so frequently found under- 

 lying the Scottish zeolites, there is often a confusedly crystalline layer of yellowish- 

 green epidote which sends off small radiating groups of spear-like crystals into the 

 scolecite. In addition to epidote there are also sometimes present in this layer 

 prehnite, garnet, albite, hornblende, and chlorite. 



Fin. 2. — Crystal of epidote from An Geania, Mull. 



Epidote occurs invariably, however, in more or less abundance, and ranges in 

 colour from blackish-green, which is rather rare at this locality, through various 

 shades of yellowish-green to pale pink or almost colourless. It occurs in radiate 

 groups of crystals which sometimes show the combination a(100), c(001), r(l01), 

 6(010), n(lll) (fig. 2). Besides occurring in intimate association with scolecite, 

 epidote is also found in cavities where that mineral is absent. For example, at the 

 north end of An Gearna, on the west slope near the summit, there is a pale, greenish- 



